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20140824

Last video on EvoluteTools PRO

It's been about a week since Evolute and I parted. But I will write another post on that soon, this one is about one last video with EvoluteTools PRO. Some time ago, Jim from TrueDynamic asked us if one could use EvoluteTools to simulate the draping of fabrics over complex shapes. The answer was yes, but of course there are limitations and this application wasn't at all something we were targeting at the time, or ever. After some back and forth communication with Jim I finally recorded a video of how it could be done. You would ask yourself - why would you need this ? Well, as it goes, complex parts made from composites (glass, aramid, carbon cloths, cored or non-cored) are most often made from several patches of fabric draped over a female or male mould. This is because a large ply will most probably never drape appropriately over a complex curved shape, so you need to split that large cloth in several overlapping patches. Even more complicated - the fiber orientation is crucial, so you can't just hack bits of cloth together just to comply to the shape of the mould. So, as far as I know, most of the time, the splitting is dictated empirically, although there are some fancy tools out there to do things automatically. Splitting the patches and designing the folds, cuts and overlaps is sometimes done as a trial and error process, using paper templates or other type of templates. Experience and geometry knowledge make this process faster and less wasteful. However, several patches in a composite part translates into a heavier part, not to mention the discontinuity of fibers. Given all this, it would be wonderful to have the ability to simulate the draping of such a fabric over the mould and do all the folds, cuts and overlaps in some software. EvoluteTools PRO can do that, but it wasn't designed to do that out of the box, so it is relatively cumbersome. For this particular video I had to write a few scripts since I needed some functionality not available in ET oob. I love working with EvoluteTools and I will really miss it, the nicest thing about ET, besides its core optimization, is the scripting interface. This means I can add various functionality to it by using its methods exposed by the scripting interface.

For example: for the video, I needed to automatically flag all the mesh corners (inside and outside) so I can create a flat contour of the unfolded mesh after many faces got deleted, and this was actually on a polymesh. All this is a piece of cake with the half-edge data structure. Just figure out your conditions and start identifying corners.

Another challenge - introduce a cut into the mesh. This was a tricky one, not because of the logic needed, but simply because during my scripting I discovered several bugs in ET and my colleagues needed several days to track down the issues and rebuild ET for me (and our customers). Again, this is not vanilla functionality in ET so far, simply scripted and hidden under various buttons just for this video. The same goes with the fiber to fiber angle analysis, a walk in the park due to the robust half-edge data structure. I will really miss scripting and working with EvoluteTools, it was like being given the keys to a 911 bi-turbo and a full gas tank. One thing, worth mentioning, I really hate my voice in all my videos, and being too focused on the functionality and not messing up other stuff, I make so many grammar mistakes, hard to swallow, hurts when I play it back.